It's simply not enough to say a baby in custody died of 'natural causes.' A neglected baby dying of malnutrition or unattended medical conditions would also die of a 'natural cause,' it may be argued.
As far as international human rights instruments go, the word 'custody' does not refer exclusively to jails or police detention centers. It also refers to all situations where people or children are kept in institutions managed by the state, except on a purely 'voluntary' basis. Thus borstals and children's homes come under this definition.
It is the responsibility of the state and those in charge of custodial institutions to ensure that basic needs of the inmates are met, including food and health care. In addition to establishing systems and benchmarks to ensure that basic services are provided it is important to organize a system of regular inspections. Further, in case of any serious mishap like death, a full and impartial inquiry must be conducted.
Questions that need to be answered in such an inquiry would include: Was the child's nutrition adequately taken care of? Did the baby suffer from a disease? Was it treated for the condition? If the baby did not respond to treatment, was it evaluated for referral abroad? Was there any neglect, and if so who was responsible?
It's simply not enough to say one has regulations on paper. They must also work on the ground. And how does one conclude a baby died of 'natural causes' before the inquiry has even begun?